1. Field of the Invention
The present invention relates generally to the field of aircraft approach landing systems. More particularly, the present invention relates to visual aircraft approach landing systems. Specifically, a preferred embodiment of the present invention relates to an approach landing system that combines lateral and vertical aircraft position indicating functions that were previously performed by multiple discrete systems. The present invention thus relates to an approach lighting system of the type that can be termed integrated.
2. Discussion of the Related Art
Historically, an important factor in air traffic control is the interaction of humans with engineering systems. Particularly important are decision-making aids to assist pilots before and during landings.
Although the rapid advances in communication and computer technology have made the automation of many aircraft crew functions possible, the final portion of an airplane's flight is still based, at least in part, on information gained by the pilot through visual landing aids (VLA). A previously recognized problem has been that existing visual landing aids systems are relatively inefficient, large, heavy, expensive to install and difficult to maintain and repair during operation.
Among currently used visual landing aids systems, there are two major families. The precision approach lighting systems (PALS, ALSF, MALSR), and their modifications, provide visual information on the direction of the runway centerline. The visual approach slope indicator systems (VASIS, PAPI, APAPI, PLASI), and their modifications, provide visual information related to glide path angle. Although the function of both systems is to provide visual confirmation of an airplane's position with respect to the runway directly before landing, these systems are designed to work independently of each other. These systems have different patterns, different operating principles and different locations.
A previously recognized problem with these systems has been that the spatial separation of the locations of the two systems causes a critical drawback. Specifically, the pilot must simultaneously monitor the two disparate systems and make crucial decisions during the same limited time span in which he must also concentrate on all the other landing procedures. Heretofore, there has been no solution to this problem. Thus, the Federal Aviation Administration (FAA) has called for an alternative approach lighting system to replace the existing precision approach lighting and visual approach slope indicator systems.
What is needed therefore is a way to integrate the functions of these two systems into a single system. However, merely integrating these two systems electrically is not sufficient because the information provided by these two systems in their current form cannot be combined without maintaining spatial separation of the lights themselves. Therefore, what is also needed (and what has not heretofore been recognized) is an integrated solution that combines the functions of these two systems physically by increasing the density of visual information that is available to an approaching pilot.
Approach lighting systems, as well as other applications such as, for example, navigation lights, call for high efficiency illumination with precisely specified requirements. These requirements can include intensity distribution across the light pattern; light pattern shape; horizontal and vertical angular distribution of light; and light color. Applications that have specific requirements such as these are called high definition (HD) lighting.
Recent progress in developing efficient light sources and manufacturing optical fiber has enabled a new kind of illumination system in which an optical fiber is used to deliver light from an illuminator to remotely located points. This new illumination system is called remote source lighting (RSL). In such a system, the distal end of the optical fiber is used to provide the light distribution required by a given application. Typically, the open end of a plastic optical fiber produces a light cone having a solid angle of between 50.degree. and 80.degree., depending on the core and cladding materials of the optical fiber. While conventional optics can be used to shape the light at the distal end of the optical fiber, problems of light loss and overly complicated lens designs have arisen. Heretofore, remote source lighting applications have been limited to areas where the combination of efficiency and precision are not required, ruling out the use of remote source light for airport approach lighting.